Rotation/oscillation converting mechanism

ABSTRACT

There is provided a mechanism for effectively converting rotary motion to a wide range of swing motion. A mechanism  1  for converting rotary to swing motion includes a rotary shaft  2,  a pivot shaft  3  and a swing element  4.  The rotary shaft  2  has an upright section  2 A connected to a motor and a slant section  2 C extending at an angle to the upright section  2 A. The swing element is mounted to the pivot shaft  3.  The slant section  2 C is positioned between a pair of confronting surfaces  4 D,  4 E of the swing element  4.  The slant section  2 C is moved on and along the confronting surfaces during rotation of the rotary shaft  2  to cause the swing element  4  to be pivoted from side to side. This movement of the swing element  4  results in pivotal movement of the pivot shaft.

FIELD OF THE INVENTION

The present invention relates to mechanisms for converting rotary motionto swing motion and vice versa.

BACKGROUND OF THE INVENTION

It is well known to provide various machines with mechanisms forconverting rotary motion to swing motion and vice versa. One suchexample is shown in FIG. 6. Specifically, a conventional mechanism 100includes a rotary shaft 101, a pivot element 102 and an ellipsoidalplate 103. Continuous rotary motion of the rotary shaft 101 is convertedto swing motion of the pivot element 102. The pivot element 102 isconical and has an inner surface 104 of an ellipsoidal section. Thepivot element 102 has a tip 102A at which the pivot element 102 ismounted to the rotary shaft 101 through a bearing assembly 105. Withthis arrangement, the rotary shaft 101 is rotated about its own axis,and the pivot element 102 is pivotable with respect to the rotary shaft101. The pivot element 102 has a central axis which is coaxial with theaxis of the rotary shaft 101 when the pivot element 102 is in itsneutral position. The central axis of the pivot element 102 is inclinedrelative to the rotary shaft 101 during swing motion. The ellipsoidalplate 103 is fixedly mounted to the rotary shaft 101 at a point offsetfrom the center of the ellipsoidal plate 103.

FIG. 7 illustrates operation of the mechanism 100. The ellipsoidal plate103 has a longitudinal end 103A. The pivot element 102 has a rightsidewall 104A and a left sidewall 104B. When the rotary shaft 101 is inits initial position as shown in FIG. 7A, the pivot element 102 is inits rightmost position wherein the longitudinal end 103A of theellipsoidal plate 103 is placed in contact with the right sidewall ofthe pivot element 102. When the rotary shaft 101 is rotated in aclockwise direction, the ellipsoidal element 103 is rotated in thedirection of the arrow in FIG. 7A and then, brought into contact withthe left sidewall 104B of the pivot element 102 as shown by dash-and-dotline in FIG. 7A.

Further rotation of the rotary shaft 101 causes the ellipsoidal plate103 to urge the pivot element 102 in a leftward direction. The pivotelement 102 is then moved into its leftmost position as shown by solidline in FIG. 7B. Thereafter, the ellipsoidal plate 103 again comes intocontact with the right sidewall 104A of the pivot element 102 and urgesthe pivot element 102 in a rightward direction. As described, the pivotelement 102 can be pivotably moved between the rightmost position, asshown by dash-and-dot line in FIG. 7B and the leftmost position, asshown by solid line in FIG. 7B during continuous rotation of the rotaryshaft 101.

The prior art mechanism 100 suffers from the following problems.Firstly, the ellipsoidal plate 103 is located between the rotary shaft101 and the pivot element 102. This arrangement makes it difficult forthe pivot element 102 to rotate through a sufficient range of swingmotion. To rotate the ellipsoidal plate 103 about the rotary shaft 101in a well-balanced manner, the axis of the rotary shaft 101 must beseparated a sufficient distance 1 (see FIG. 7B) from the end 103B of theellipsoidal plate 103. There is thus a limitation on the range of swingmotion of the pivot element 102.

Secondly, rotary motion of the rotary shaft 101 can only partly beconverted to swing motion of the pivot element 102. For example, theellipsoidal plate 103 is kept out of contact with the inner sidewall ofthe pivot element 102 when the ellipsoidal plate 103 is moved betweenthe position shown by solid line in FIG. 7A and the position shown bydash-and-dot line in FIG. 7A. During this movement of the ellipsoidalplate 102, no rotary motion is converted to swing motion of the pivotelement 102. The mechanism 100 is thus unable to effectively convertrotary motion to swing motion.

It is, therefore, an object of the present invention to provide amechanism which is simple in structure and can convert rotary motion toa wide range of swing motion. It is another object of the presentinvention to provide a mechanism which allows effective conversionbetween rotary motion and swing motion.

SUMMARY OF THE INVENTION

The present invention provides a mechanism for converting rotary motionto swing motion, which includes a rotary shaft having a central axisabout which the rotary shaft is rotated in one direction, a pivot shafthaving an axis about which the pivot shaft is rotated in alternatedirections, and a swing element mounted to the pivot shaft. The rotaryshaft has a slant section inclined relative to the central axis, and theswing element has a pair of confronting surfaces between which the slantsection of the rotary shaft is positioned. With this arrangement, theslant section of the rotary shaft is rotated about the central axis ofthe rotary shaft during rotation of the rotary shaft. The slant sectionis brought into contact with a selected one of the confronting surfacesof the swing element in response to the direction of rotation of therotary shaft. As a result of this contact, the swing element is inclinedfrom its upright position. The swing element is pivotably moved inalternate directions during rotation of the rotary shaft. Also, thepivot shaft is pivotally moved with the swing element. The presentinvention can convert rotary motion to swing motion with such a simplestructure.

In one embodiment, the pivot shaft is located in a side-by-side relationto the proximal end of the slant section and extends in a directionperpendicular to the central axis of the rotary shaft. By thisarrangement, the angle of inclination of the slant section of the rotaryshaft determines the range of swing motion of the swing element (as wellas the range of pivotal motion of the pivot shaft). This range canreadily be changed by increasing or decreasing the angle of inclinationof the slant section. This configuration also allows the swing elementto be rotated through a wider range of swing motion.

In one embodiment, the two confronting surfaces of the swing element arespaced a slight distance from the slant section of the rotary shaft.This configuration permits the slant section to be held in contact withthe confronting surfaces during a substantial part of movement of therotary shaft and thus, provides effective conversion between rotary andswing motion without any transmission loss.

In another embodiment, the confronting surfaces of the swing elementextend generally parallel to the slant section of the rotary shaft. Thisresults in an increase in the contact surface area between the slantsection and the confronting surfaces. Such an increased contact surfacearea ensures constant pivotal movement of the swing element and thus,stable conversion between rotary motion and swing motion.

In one embodiment, the swing element has a U-shaped section and includesa pair of confronting sidewalls in the form of a plate and a bottom wallconnected to the lower end of the confronting sidewalls. The bottom wallhas an opening through which the slant section of the rotary shaft isinserted between the confronting sidewalls of the swing element.

The opening is defined substantially centrally in the bottom wall of theswing element.

The bottom wall of the swing element extend in a direction perpendicularto the central axis of the rotary shaft.

The pivot shaft and a support shaft cooperatively support opposite sidesof the bottom wall of the swing element. The support shaft extends in asubstantially coaxial relation to the pivot shaft.

The pivot shaft and the support shaft are secured within the bottom wallof the swing element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a mechanism for converting rotary motion toswing motion, made according to one embodiment of the present inventionand secured to a motor;

FIG. 2 is a side view of the mechanism with a swing element in itsneutral position;

FIG. 3 is a view similar to that of FIG. 2, showing that the swingelement is rotated through a full range of swing motion;

FIG. 4A is a perspective view of the mechanism, with the swing elementpivoted to its leftmost position;

FIG. 4B is a view similar to that of FIG. 4A, but with the swing elementheld in its neutral position;

FIG. 4C is a view similar to that of FIG. 4A, but with the swing elementpivoted to its rightmost position;

FIG. 5A is a top plan view of the mechanism, with the swing elementpivoted to its leftmost position;

FIG. 5B is a view similar to that of FIG. 5A, but with the swing elementheld in its neutral position;

FIG. 5C is a view similar to that of FIG. 5A, but with the swing elementpivoted to its rightmost position;

FIG. 6 is a perspective view of a conventional mechanism for convertingrotary motion to swing motion; and

FIGS. 7A and 7B are sectional views of the conventional mechanism.

PREFERRED MODES FOR CARRYING OUT THE INVENTION

FIGS. 1 to 3 illustrate a mechanism 1 for converting rotary motion toswing motion, made according to one embodiment of the present invention.As shown, the mechanism 1 generally includes a rotary shaft 2 rotatableabout its central axis, a pivot shaft 3 pivotable about its axis, and aswing element 4 through which the rotary shaft 2 and the pivot shaft 3are interconnected.

The rotary shaft 2 has a proximal or upright section 2A extending alongthe central axis of the rotary shaft 2. The rotary shaft 2 is connectedto a motor 10 which in turn, imparts continuous rotary motion to therotary shaft 2. The upright section 2A is rotatably supported within ahousing (not shown) through a bearing assembly 5.

The rotary shaft 2 has a bent 2B and a distal or slant section 2Cextending from the upright section 2A through the bent 2B. The slantsection 2C is inclined at an angle α to the central axis of the rotaryshaft 2.

The swing element 4 has a U-shaped section. The swing element 4 includesa round bottom wall 4A and a pair of confronting plates or sidewalls 4B,4C extending from the bottom wall 4A in a generally parallelrelationship. The slant section 2C of the rotary shaft 2 is locatedbetween the two confronting sidewalls 4B, 4C. The distance between thetwo confronting sidewalls 4B, 4C is slightly greater than the diameterof the rotary shaft 2. The confronting sidewalls 4B, 4C have respectiveinner surfaces 4D, 4E oriented in a confronting relation to oppositesides of the slant section 2C. An opening 4F is defined substantiallycentrally in the bottom wall 4A and extends into part of the sidewalls4B, 4C. The slant section 2C of the rotary shaft 2 extends through theopening 4F and is disposed between the confronting sidewalls 4B, 4C. Theconfronting inner surfaces 4D, 4E extend parallel to the slant section2C and are slightly spaced from the slant section 2C.

When the rotary shaft 2 is rotated, the slant section 2C comes intocontact with one of the confronting inner surfaces 4D, 4E of the swingelement 4, as will later be described in more detail with reference toFIGS. 4 and 5. Then, the slant section 2C is slidably moved on and alongthe inner surfaces 4D, 4E. This imparts swing motion to the swingelement 4. The swing element 4 is pivoted alternately from its neutralposition to opposite sides. The range of pivotal movement of the swingelement 4 at each side is equal to the angle α of inclination of theslant section 2C (see FIG. 3). Thus, its range can readily be changed byincreasing or decreasing the angle α of inclination of the slant section2C. Also, this configuration allows the swing element 4 to be rotatedthrough a wider range of swing motion than that of the prior artmechanism. The swing element 4 can be pivoted at any angle between zeroand 80 degrees at each side (total range of swing motion is thus 160degrees). In the illustrated embodiment, the angle of inclination of theslant section 2C is 80 degrees.

The swing element 4 is supported at its opposite ends by the pivot shaft3 and a support shaft 6 so that the swing element 4 can be pivoted aboutthe axes of the pivot shaft 3 and the support shaft 6. The pivot shaft 3has an end 3A secured within one end of the bottom wall 4A of the swingelement 4. Similarly, the support shaft 6 has an end 6A secured withinthe other end of the bottom wall 4A of the swing element 4. The pivotshaft 3 faces with and is coaxial with the support shaft 6. The pivotshaft 3 and the support shaft 6 are pivotably supported within thehousing (not shown) through respective bearing assemblies 7, 8. The bent2B (or the proximal end of the slant section 2C) of the rotary shaft 2is positioned in a side-by-side relationship to the pivot shaft 3 andthe support shaft 6. This arrangement permits the swing element 4 to bepivoted at an angle equal to the angle α of inclination of the slantsection 2C of the rotary shaft 2.

The pivot shaft 3 is connected, for example, to a working tool (notshown) to be pivoted. The pivot shaft 3 is pivoted at the same angle asthe swing element 4. The pivotal movement of the pivot shaft 3 is thentransmitted to such a working tool.

Operation of the mechanism 1 will next be described with reference toFIGS. 4 and 5.

FIGS. 4B and 5B show the swing element 4 in its neutral position whereinthe slant section 2C of the rotary shaft 2 and the pivot shaft 3 lie ona common vertical plane, and the swing element 4 vertically extendsalong the central axis (the axis of the upright section 2A). With theswing element 4 in its neutral position, the slant section 2C may bedirected toward the pivot shaft 3 (as shown by broken line in FIG. 4B)or the support shaft 3 (as shown by dash-and-dot line in FIG. 4B). Inthe following description, the term “initial position” is used to meanthat the slant section 2C is directed toward the pivot shaft 3.

With the swing element 4 in its initial position, the rotary shaft 2 isrotated in a counterclockwise direction as seen in FIGS. 4 and 5. Thiscauses the slant section 2C to be pivoted to the right while the slantsection 2C is slidably moved on and along the inner surface 4D of thesidewall 4B. As the angle of inclination of the slant section 2Cgradually increases when seen in the axial direction of the pivot shaft3, the swing element 4 is also gradually moved to the right. Thismovement causes the pivot shaft 3 to be rotated in a clockwisedirection.

As shown in FIG. 4C, the swing element 4 reaches its rightmost positionwhen the slant section 2C is oriented perpendicular to the pivot shaft3. The swing element 4 is inclined at an angle equal to the angle α ofinclination of the slant section 2C. Also, the pivot shaft 3 is pivotedclockwise at an angle equal to the angle α of inclination of the slantsection 2C.

Further rotation of the rotary shaft 2 causes the slant section 2C to bemoved toward its neutral position while the slant section 2C is slidablymoved on and along the inner surface 4E of the sidewall 4C. The swingelement 4 is gradually raised as the angle of inclination of the slantsection 2C gradually decreases when seen in the axial direction of thepivot shaft 3. At this time, the pivot shaft 3 is rotated in acounterclockwise direction. The swing element 4 is returned to itsneutral position when the slant section 2C is moved to the positionshown by dash-and-dot line in FIG. 4B.

Further counterclockwise rotation of the rotary shaft 2 causes the swingelement 4 to be rotated to the left, in a manner opposite to the mannerin which the swing element 4 is rotated to the right. As the slantsection 2C is inclined to the left, the swing element 4 is rotated tothe right. This causes counterclockwise rotation of the pivot shaft 3.The swing element 4 is leftwardly inclined at the maximum angle (−α)when the slant section 2C reaches a position as shown in FIG. 4A. Themaximum angle of swing motion of the pivot shaft 3 is also −α. The slantsection 2C is thereafter moved back toward its initial position.

This movement causes the swing element 4 to be moved to its uprightposition. Also, the pivot shaft 3 is rotated in a clockwise direction.When the slant section 2C is returned to its initial position, one cycleof operation is completed (the swing element is pivoted at a total angleof 160 degrees).

As thus far described, one revolution of the rotary shaft 2 causes thepivot shaft 3 to be pivoted from side to side at a total angel of 2×α.The angle of swing motion of the pivot shaft 3 is equal to the angle αof inclination of the slant section 2C. The angle of swing motion of thepivot shaft 3 can thus be readily changed by increasing or decreasingthe angle α of inclination of the slant section 2C. Advantageously, thisarrangement allows the swing element 4 to be rotated through a widerrange of swing motion. In the illustrated embodiment, the slant section2C can be inclined at an angle of zero to 80 degrees. Also, the pivotshaft 3 can be pivoted at an angle of zero to 160 degrees.

Rotary motion of the rotary shaft 2 can be fully converted to swingmotion of the pivot shaft 3 (or the swing element 4). This is becauseduring rotation of the rotary shaft 2, the slant section 2C is kept incontact with either the inner surface 4D or the inner surface 4E of theswing element 4. This configuration substantially constantly impartsswing motion to the swing element 4 without any loss of powertransmission. The present invention is thus able to effectively convertrotary motion to swing motion.

The mechanism 1 generally requires only three parts, namely, rotaryshaft 2, pivot shaft 3 and swing element 4. Thus, the mechanism 1 issimple in structure, is easy to manufacture, is inexpensive, andprovides high performance.

In the illustrated embodiment, the mechanism 1 is used to convert rotaryto swing motion. Alternatively, the mechanism can be used to convertswing to rotary motion. It is also to be understood that after rotarymotion of the rotary shaft 2 is converted to swing motion of the swingelement 4, such swing motion can be transmitted not through the pivotshaft 3, but directly from the swing element to an article to bepivoted.

1. A mechanism for converting rotary motion to swing motion, comprising:a rotary shaft having a central axis, said rotary shaft being rotated inone direction about said central axis; a pivot shaft having an axis,said pivot shaft being rotated in alternate directions about said axis;and a swing element mounted to said pivot shaft, said rotary shaftincluding a slant section inclined relative to said central axis of saidrotary shaft, said swing element including a pair of confrontingsurfaces, said slant section of said rotary shaft being positionedbetween said pair of confronting surfaces of said swing element.
 2. Themechanism of claim 1, wherein said slant section has a proximal end,said pivot shaft is positioned in a side-by-side relation to saidproximal end of said slant section and extends in a directionperpendicular to said central axis of said rotary shaft.
 3. Themechanism of claim 1, wherein said pair of confronting surfaces of saidswing element are positioned at opposite sides of said slant sectionwith a slight clearance therebetween.
 4. The mechanism of claim 1,wherein said pair of confronting surfaces of said swing element extendgenerally parallel to said slant section of said rotary shaft.
 5. Themechanism of claim 1, wherein said swing element has a U-shaped sectionand includes a pair of confronting sidewalls in the form of a plate, abottom wall and an opening defined in said bottom wall, said slantsection of said rotary shaft being inserted through said opening andpositioned between said pair of confronting sidewalls.
 6. The mechanismof claim 5, wherein said opening is defined substantially centrally insaid bottom wall of said swing element.
 7. The mechanism of claim 5,wherein said bottom wall of said swing element extends in a directionperpendicular to said central axis of said rotary shaft.
 8. Themechanism of claim 5, further comprising a support shaft extending in ancoaxial relation to said pivot shaft, said pivot shaft and said supportshaft being cooperative to support opposite sides of said bottom wall ofsaid swing element.
 9. The mechanism of claim 8, wherein said pivotshaft and said support shaft are secured within the bottom wall of saidswing element.